The invention disclosed herein relates generally to automated mail sorting and more particularly, an apparatus and method for weighing mail in motion, or on the fly, while maintaining the mail in a vertical orientation.
The processing and handling of mailpieces consumes an enormous amount of human and financial resources, particularly if done manually. In addition to the postal service, the processing and handling of mailpieces occurs at each and every business or site where communication via the mail delivery system is utilized. Various pieces of mail generated by multiple departments and individuals within a company need to be collected, sorted, addressed and franked as part of the outgoing mail process. Additionally, incoming mail needs to be collected and sorted efficiently to ensure that it gets to the addressee in a minimal amount of time. Since much of the mail being conveyed through the mail system is critical in nature, it is imperative that the processing and handling of both the incoming and outgoing mailpieces be efficient and reliable so as not to impact negatively the operation of the business.
In view of the above, various automated mail handling machines have been developed for processing mail (removing individual pieces of mail from a stack and performing subsequent actions on each individual piece of mail). However, in order for these automatic mailing machines to be effective, they must process and handle xe2x80x9cmixed mailxe2x80x9d. The term xe2x80x9cmixed mailxe2x80x9d is used herein to mean sets of intermixed mailpieces of varying size (postcards to 9xe2x80x3 by 12xe2x80x3 flats), thickness, and weight. In addition, the term xe2x80x9cmixed mailxe2x80x9d also includes stepped mail (i.e., an envelope containing an insert which is smaller than the envelope to create a step in the envelope), tabbed and untabbed mail products, and mailpieces made from different substrates. Thus, the range of types and sizes of mailpieces which must be processed is extremely broad and often requires trade-offs to be made in the design of mixed mail feeding devices in order to permit effective and reliable processing of a wide variety of mixed mailpieces.
In known mixed mail handling machines which separate and transport individual pieces of mail away from a stack of mixed mail, the stack of mixed mail is first loaded onto some type of transport system for subsequent sorting into individual pieces of mail. Typically, it is preferable to transport a mailpiece in a vertical orientation (on its bottom edge) in order to facilitate the manipulation of individual mailpieces. In systems handling outgoing mail, it is necessary to affix the individual mailpieces with the proper postage. To calculate proper postage it is necessary for the system to determine the distance and manner in which a mailpiece is being sent in addition to its size and weight.
Various scanning and sorting technologies have been implemented as part of automated mail handling systems to determine the distance and manner in which a mailpiece is being sent along with its size. However, prior art systems of mail handling do not adequately provide for the accurate calculation of the weight of a particular mailpiece as it is being processed. To weigh a mailpiece as quickly and accurately as possible, it is desirable to minimize the amount of vibration while weighing the mailpiece. The method used in numerous contemporary systems is to stop the transport of the mailpiece during weighing. While this reduces the vibration caused by the transport, it also increases the cycle time of the mailpiece due to the time required to decelerate the mailpiece, wait for the transport to settle, measure the weight of the mailpiece and accelerate the mailpiece out of the system. Still other contemporary mail handling systems require that the weighing process be performed on a horizontally oriented mailpiece.
Although weighing mailpieces while in transport reduces the need for stopping the system, certain situations require the mail process to be halted. For example, if the weight of the mailpiece is very close to the postal weight break, the accuracy needed to prevent an inaccurate weight classification may require more time and scale stability than can be provided a moving transport. In such a case, there are three choices: 1) apply postage that may be incorrect, 2) acknowledge the incorrectly weighed mailpiece and divert it away from the stack of mail, or 3) stop the transport and wait for the scale to stabilize and then reweigh the mailpiece. The present invention provides for the third scenario, i.e., stop-on-demand weighing. For example, first class letter rates increase by the ounce. Thus, the postal weight breaks are at one ounce, two ounces, three ounces and so forth. When the system weighs a mailpiece, if the postal weight break is within the weight of the mailpiece plus or minus the weighing system""s margin of error, the mailpiece is reweighed. This feature allows the system to automatically stop when more precise measurements are needed.
One of the problems of the prior art is that an apparatus is not available for the accurate calculation of the weight of a mailpiece while the mailpiece is in a vertical orientation, that is, on a mailpiece""s bottom edge. Another problem of the prior art is that mechanical vibrations introduced by the system generate inaccurate weight measurements. Yet another problem of the prior art is that the weighing process requires the re-orientation of the mailpiece to be weighed or a stoppage in the mail handling process in order to generate an accurate weight measurement. Therefore, a method is needed to provide for the efficient measurement of the weight of a mailpiece while maintaining the vertical orientation of the mailpiece.
Utilized as part of a complete system of automated mail handling, the present invention overcomes the disadvantages of the prior art by providing an apparatus and method for accurately measuring the weight of vertically oriented mailpieces without stopping the mail handling process. In a currently preferred embodiment of the invention, a bottom belt transport oriented parallel to the base and with vertical baffles is mounted on a weighing mechanism (load cell) which in turn is mounted on the base of the apparatus. In this configuration, mailpieces enter the transport in a vertical orientation and are biased against the bottom of the belt by gravity. This eliminates the need for ski rollers, which create vibrations, as they engage and disengage the mailpieces. Only two rotating elements are required in this transport, which also reduces vibration. By minimizing vibration, a measurement of the weight of the mailpieces can be determined more accurately and quickly, thereby increasing overall throughput of the apparatus.
In another currently preferred embodiment, a bottom belt transport, also oriented parallel to the base, is mounted on a pair of load cells which, in turn, are independently mounted to the base of the apparatus. Again, mailpieces enter the transport in a vertical orientation and are biased against the bottom of the belt by gravity. A first load cell is located at the input end of the apparatus, and a second load cell is located at the output end of the apparatus. The signals received from the first and second load cells are combined via a trim balance circuit which, in turn, transmits the weight to the main processing system of the mail handling system in which the inventive apparatus is installed.
In yet another preferred embodiment, the vertical baffles are held in place by baffle support brackets which, in turn, are mounted directly to the base of the apparatus. Isolating the baffles from the transport and load cells reduces vibration at the load cells by limiting the vibration caused by mailpieces impacting the baffles. By minimizing vibration, a measurement of the weight of the mailpieces can be determined more accurately and quickly, thereby increasing overall throughput of the apparatus. Vertical baffles held in place by baffle support brackets may be utilized in apparatus using either one or a plurality of load cells to measure the weight of the mailpiece in the transport.
In yet another preferred embodiment, the transport belts are oriented perpendicular to the base. The entire system is mounted on top of a structural pillar connected to the base, thus making the entire system suspended in air. A single load cell has its weighing surface oriented parallel to the transport belts, or perpendicular to the base. Any vibrations or oscillations in the mechanics of the system would be minimized because they would not occur in the same vector as the weight of the mailpiece.
Thus, an advantage of the present invention is that it may accurately weigh mailpieces in a vertical orientation, or on their bottom edge. Another advantage is that the present invention reduces the overall vibration present in the system, thereby providing a more accurate calculation of weight. Yet another advantage of the present invention is that it does not require the transport to be stopped in order to calculate the weight of a mailpiece.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The aforementioned advantages are illustrative of the advantages of the various embodiments of the present invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.